Numerical Affordance Influences Action Execution: A Kinematic Study of Finger Movement

Abstract

Humans represent symbolic numbers as oriented from left to right: the mental number line (MNL). Up to now, scientific studies have mainly investigated the MNL by means of response times. However, the existing knowledge on the MNL can be advantaged by studies on motor patterns while responding to a number. Cognitive representations, in fact, cannot be fully understood without considering their impact on actions. Here we investigated whether a motor response can be influenced by number processing. Participants seated in front of a little soccer goal. On each trial they were visually presented with a numerical (2, 5, 8) or a non-numerical ($) stimulus. They were instructed to kick a small ball with their right index toward a frontal soccer goal as soon as a stimulus appeared on a screen. However, they had to refrain from kicking when number five was presented (no-go signal). Our main finding is that performing a kicking action after observation of the larger digit proved to be more efficient: the trajectory path was shorter and lower on the surface, velocity peak was anticipated. The smaller number, instead, specifically altered the temporal and spatial aspects of trajectories, leading to more prolonged left deviations. This is the first experimental demonstration that the reaching component of a movement is influenced by number magnitude. Since this paradigm does not require any verbal skill and non-symbolic stimuli (array of dots) can be used, it could be fruitfully adopted to evaluate number abilities in children and even preschoolers. Notably, this is a self-motivating and engaging task, which might help children to get involved and to reduce potential arousal connected to institutional paper-and-pencil examinations.

Compatibility between object size and response side in grasping: the left hand prefers smaller objects, the right hand prefers larger objects

“…Although most studies have examined interactions between numerical information and motor-related spatial coding (e.g., Andres et al, 2004 ; Andres et al, 2008 ; Lindemann et al, 2007 ; Namdar et al, 2014 ; Namdar & Ganel, 2018 ; Rugani, Betti & Sartori, 2018 ; Rugani et al, 2017 ; Badets & Pesenti, 2010 ; Ranzini et al, 2011 ), similar interactions have also been observed for other magnitude domains. For example, when participants reached out to grasp a wooden block, their movements had a larger grip aperture after reading a word representing a larger object (e.g., apple) than reading a word representing a small object (e.g., grape Glover et al, 2004 ), indicating interactions between (conceptual) object size and reach-to-grasp movements (see also Gentilucci et al, 2000 ; Glover & Dixon, 2002 ).…”

Peer Review #1 of "Compatibility between object size and response side in grasping: the left hand prefers smaller objects, the right hand prefers larger objects (v0.1)"

“…Although most studies have examined interactions between numerical information and motor-related spatial coding (e.g., Andres et al, 2004;Andres et al, 2008;Lindemann et al, 2007;Namdar et al, 2014;Namdar and Ganel, 2018;Rugani et al, 2018;Rugani et al, 2017;Badets and Pesenti, 2010;Ranzini et al, 2011), similar interactions have also been observed for other magnitude domains. For example, when participants reached out to grasp a wooden block, their movements had a larger grip aperture after reading a word representing a larger object (e.g.…”

Approach direction and accuracy, but not response times, show spatial-numerical association in chicks

“…In a dual task, which required estimating whether a number was smaller or bigger than five while moving a block in peripersonal space, adults while processing a smaller number placed a cube leftward—and rightward while processing larger numbers [ 8 ]. In executing an uncommon action, such as flicking a ball with the index finger toward one of two lateral goals upon detecting a visual stimulus, participants flicked leftward in response to small numbers and rightward when responding to large ones [ 9 ]. Overall, this evidence shows an intertwined interaction between numbers and action influence.…”

“…After the generation of small numbers, the participants turned left—and after the generation of larger numbers they turned right [ 10 ]. Thus, the association between numbers and space is not limited to the speed of action executions—instead it also affects action selection [ 9 , 11 , 12 ]. Nevertheless, an open question is whether an experimental paradigm designed to measures the SNA by action selection might assess it also by response times and vice-versa.…”